(Cat? OR feline) AND NOT dog?
Cat? W/5 behavior
(Cat? OR feline) AND traits
Cat AND charact*

This guide provides a more detailed description of the syntax that is supported along with examples.

This search box also supports the look-up of an IP.com Digital Signature (also referred to as Fingerprint); enter the 72-, 48-, or 32-character code to retrieve details of the associated file or submission.

Concept Search - What can I type?

For a concept search, you can enter phrases, sentences, or full paragraphs in English. For example, copy and paste the abstract of a patent application or paragraphs from an article.

Concept search eliminates the need for complex Boolean syntax to inform retrieval. Our Semantic Gist engine uses advanced cognitive semantic analysis to extract the meaning of data. This reduces the chances of missing valuable information, that may result from traditional keyword searching.

Separation of Polymers from Solution

Publishing Venue

The IP.com Prior Art Database

Abstract

The high temperatures and the associated high pressures for devolatization of polymer solutions could be avoided by heating and flashing the polymer solution in more than one and preferably in two stages. Only part of the solvent is flashed off in the first stage so that the temperature does not drop too low, then the polymer rich solution is heated in another heater before the final flash.

Country

Canada

Language

English (United States)

This text was extracted from a Microsoft Word document.

This is the abbreviated version, containing approximately
49% of the total text.

Separation
of Polymers from Solution

The process described below relates to the means of
recovering polymers from their solution by heating the solution and flashing
off the solvent in two steps. Many
polymers are prepared by polymerizing a monomer in the presence of a solvent
under conditions needed for the polymer to remain in solution. There are various reasons for using solvent
in the industrial production of polymers.
For example, in polymerizing ethylene to polyethylene the heat of
polymerization is high and the solvent provides a heat sink thus enabling good
process control and preventing a runaway reaction. At any rate, the polymer leaves the reactor as a solution and
must be separated from the solvent to be recovered.

The equipment for separating the polymer from the solution
should be simple, reliable and inexpensive.
The separation process should not contaminate either the recovered
polymer or the solvent with byproducts, decomposition products or other
undesirable materials.

There are known processes for recovering polymers from their
solution. If the polymer such as
polyethylene is not soluble in the solvent at low temperatures, the solution
can be cooled to precipitate the polymer.
Alternately, an addition of a non solvent can also precipitate the
polymer. The precipitated polymer can
then be recovered by filtration or centrifugation. This method is widely used for recovering polymers from their
solution on a small scale, in pilot plants and laboratory units, for
example. On a large scale, however, the
process is slow, costly and complicated.
It is not used.

Another option is to heat the polymer solution in a heat
exchanger and then reduce the pressure in one or more stages. Upon the pressure reduction, the solvent
adiabatically flashes off and the polymer is separated from the solvent vapors
in a settling vessel. Although this
process works and is commercially used it has many draw-backs. In each flashing stage the temperature
decreases and the initial solution temperature must be high enough to yield in
the last stage molten polymer with a low content of solvent. The rate of heat transfer in the heat
exchanger is low because of the high viscosity of polymer solutions and low
thermal conductivity. Also, in order to
obtain the molten polymer in the final flashing step, the initial temperature
must be quite high. Thus the heat
exchanger and temperature difference between the wall and process stream must
be large. To achieve high wall
temperatures requires expensive and difficult to run heating systems such as
Dowtherm® or very high pressure steam.
High wall temperature also requires high process pressures to prevent
the solvent from flashing in the heat exchanger and may cause degradation of
the product or of the solvent.

US Patent 5,037,955 to Dow describes a multi-section heat
exchanger suitable for heating viscous polymer solutions. The improvement is in controlling each
section separat...